X-rays and the statues eyes

left eyeIn a previous post, we told you that the two wooden heads were going to be X-rayed and CT-scanned, alongside with some other artifacts from the Lab.

In this post we will deal with what we learned about the wooden heads’ eyes from the X-radiographs only.

A lot of our readers will probably know what X-rays are, for they may have experienced them in a hospital. X-rays are also successfully used in Art and Archaeology (for a general overview and some examples, see SCHREINER et al, “X-rays in Art and Archaeology – An overview). The principle of the X-ray is to expose a material to x-ray energy of a particular wavelength. According to the molecular weight of the material, the x-rays will, or won’t, be allowed to go completely through it. The energy that does penetrate passes through to a detector.

In digital radiography, the data is then processed by a computer and, eventually, we obtain a picture where dense (high molecular weight) materials appear white and lighter ones (low molecular weight) are black.

X-ray photograph of E17911

X-ray photograph of E17911 – We can see a lot of termite tunnels and the big hole inside the head, on the right-hand side, and the shining eyes.

E17911, in profile - This picture allows us to see more clearly the structure of the eyes.

E17911, in profile – This picture allows us to see more clearly the structure of the eyes.

New Picture (2)

E17910 – Also helpful about the inserting of the eyes.

In these radiographs, we clearly see the structure of the inlaid eyes. In fact, those eyes are quite similar to those studied at the Louvre Museum on Kay’s statue (ZIEGLER, Les statues égyptiennes de l’Ancien Empire, Musée du Louvre, 1997, p.256). This statue is from the Vth Dynasty, not so far in time from our heads.

Eventually, we can conclude that the eyes are made of a metallic sheet soldered in the back, which is flat. It is shell-shaped and the hippo ivory is inserted inside. Then the black pupils (made of obsidian?) are placed in the ivory, maintained inside by an adhesive (resin ? plaster ?).

New Picture (3)

X-ray radiography photograph of Kay’s statue eyes (from ZIEGLER, 1997, p.256).

Structure of Kay's eyes (from ZIEGLER, 1997, p.259); the back of the metallic part is flat and the edges were folded so as to form the eyelids.

Structure of Kay’s eyes (from ZIEGLER, 1997, p.259); the back of the metallic part is flat and the edges were folded so as to form the eyelids.

Structure of Kay's eyes and identification of the materials we have on Adu's eyes (from ZIEGLER, 1997, p.259)

Structure of Kay’s eyes and identification of the materials we have on Adu’s eyes (from ZIEGLER, 1997, p.259)

 

 

 

 

 

 

 

 

 

 

Fortunately, the Penn Museum has some inlaid eyes in storage, allowing us to figure out more clearly what we have on the heads.

New Picture (7)

The eye n.E6789B – Limestone and obsidian.

 

Back of the eye n.E12905A - Copper alloy.

Back of the eye n.E12905A – Copper alloy.

 

 

 

 

 

 

 

 

 

 

 

Again, fortunately for us (yes, fortunately!), the Louvre Museum has a very interesting statue, also from the Old Kingdom, with missing eyes. This statue of a nobleman named Tcheti informs us on how the inlaid eyes were inserted into the wood.

Tcheti statue, Louvre Museum n.E11566 - Detail of the missing eyes.

Tcheti statue, Louvre Museum n.E11566 – Detail of the missing eyes.

We can see that a hole was cut in the wood, fitting the eyes’ size. We can suppose that an adhesive was used to prevent the eyes from falling off the statue.

As you can see, a conservation intervention, apart from treating the objects, can also allow us to study them more closely and to know them better.

We will talk about the CT-scan in a next post and, in the meantime, you’re more than welcome to visit us at the Lab or to post a comment below !

 

Let’s focus on the eyes.

eye

In a former post we saw that a conservator has to gather clues about an object’s past and do a lot of bibliographical research. Now let’s talk about the materials themselves and the amazing eyes of these two wooden heads.

During these last few weeks we have been busy trying to identify the materials used to make the eyes; we knew that there were three of them, one for the outer line (or eyelid), a second for the white part, and the third one for the black pupil. We first observed the eyes under a binocular microscope, which is the easiest way for a conservator to have a close look at an object.

Leica Picture

Wood is missing around the eyes, but it allows us to see more of the metal !

Leica Picture

Here is a pink-golden layer of copper that we can identify through the corrosion layers.

 

The material used for the eyelids was immediately identified as a copper alloy because of the green corrosion products observed on the surface. Moreover we can see the metallic pink-golden surface of the copper here and there. However, the metal could have also been silver with some copper impurities; indeed when two metals are combined or in contact with each other in a burial environment, the less precious metal preferentially corrodes (also called galvanic corrosion).

To know more about the chemical composition of this alloy, we carried out X-ray fluorescence analysis (XRF), with the portable XRF device of the Lab.

Here are what the results look like:

E17911 - eye - bluefilter

Those peaks indicate what kind of elements we have in the metal. We learned that this is an arsenic-copper alloy, which is well-known for Egyptian artifacts. The other elements can be impurities in the metal or due to the burial environment of the objects.

Concerning the white material, the first thing we observed under the microscope was the lines in the material.

Leica Picture

Some detail of the lines.

IC800516

A clue for us was that we don’t see the lines across the entire surface, as we can see on the picture on the right (near the upper part of the pupil).

We first wondered if these lines indicated elephant ivory, since elephant ivory has unique features called Schreger lines. However, the lines in the whites of the eyes do not look like Schreger lines, which look more like cross-hatching. That’s why we then thought about tool marks; indeed, the Egyptian sometimes marked the material they used to make the white of inlaid eyes, to make them look more realistic. We quickly abandoned this theory because the pattern on the eyes is too regular and not spread across the entire surface.

So we returned to the idea that the material might be ivory, but what kind of ivory? We were lucky that our department recently acquired a complete set of ivory samples, so we could compare directly. It turned out that our eyes are made of hippo ivory. XRF analysis also revealed that the white is composed of calcium, which is coherent for ivory.

ivory

This is elephant ivory.

 

IC800527 - Copy

Here is an example of what hippo ivory looks like, with the entire surface covered with lines.

IC800522

Here is an area of the hippo ivory where we can see the limit between the lines and a smooth part.

Concerning the material used to make the black of the eyes, a few paths could be followed. According to the literature, Egyptians used obsidian, glass with a black substance on the back, or other black materials for the inlaid eye pupils. The microscopic observation of the wooden statue eyes revealed that the black material is translucent with tiny bubbles. This structure could indicate obsidian, which is a natural glass. Moreover, the Penn Museum has several spare eyes in storage; comparison with these known references confirmed that the pupils of the wooden heads are indeed made from obsidian.

Leica Picture

We will know more about the structure of the eyes by next week, since this Friday the heads are going to be X-rayed and CT-scanned !

 

First step for the heads

Last week I introduced you to two wooden statue heads that I’m working on and promised to share the step by step process of their conservation.

laura blog 2 image3

A first step in understanding these objects is gathering information about their past. As we said in the previous post, they are from Dendera and were discovered in 1898. The other questions were: Who discovered them? How and when did they arrive in Philadelphia? And more…

To address these questions, the best place to begin is the Museum Archives. I first checked Clarence Fisher’s field notebooks, since we know that he excavated in Dendera for the museum from 1915-1918, continuing the work begun by Charles Rosher and Flinders Petrie. An afternoon looking at (all!) of his notebooks revealed no leads. The other possibility was to refer to Petrie’s own field records; and here I found reference to the heads, or more precisely the “statuettes”, noted in his field notebook.

This page notes the “2 statuettes” at the foot of the coffin.
From Petrie Notebook n.15, p.30, courtesy and copyright of the Petrie Museum of Egyptian Archaeology, UCL.

That mystery solved, we moved onto the next one. Included in the storage drawer with the wooden heads, we found a note indicating “2 wooden statuettes nearly consumed by white ants”.

laura blog 2 image2After a little more digging, I found that this was a quote from Petrie’s publication about Dendera, on p.10, paragraph 2…and the rest is still meaningless to us! In this publication Petrie indicates that the heads came from a secondary burial, belonging to a woman, under Adu II’s own funerary chamber.

Moreover, it unveiled a new clue: Petrie wrote that he discovered “statuettes” and not only their heads. That could imply the fact that they were still complete statues at the time of the excavation. It is possible that they were in such a poor condition that the archaeologist left the bodies and only took the heads. We definitely do not have any more parts of these statues in our collection – after checking, no “spare bodies” are registered in the Egyptian storerooms of the Penn Museum.

All of this may seem to be only details but it is essential information for a conservator: the fact that W.M.F. Petrie discovered the heads is highly interesting, because he most likely treated them in the field. He published a book where he explains his practical way of applying a “first-aid” treatment to damaged artifacts (Methods and aims in Archaeology, 1904) which may provide critical information for us! Indeed, knowing this will allow the conservator to be aware of what kind of material was added to the original object and how to deal with it.

My investigation into these old treatment materials will be the topic of a post to come!

 

About two wooden Egyptian heads…

“You have a wonderful job!” It’s a sentence that a conservator often hears. But what is really this incredible job? I propose to you to have a closer look at what a conservator usually does by following step by step the conservation of two artifacts recently arrived in the Artifact Lab.

Laura blogpost1Not really the glamorous objects you imagine when you think about Ancient Egypt, right? But they can reveal so many things to us.

Let’s begin with all what we knew when they arrived in the Lab: these artifacts are two Egyptian wooden statue heads. They bear remains of polychromy (blue and red painting) and have inlaid eyes. In their storage drawer were three labels: one quoting a publication about Dendera (the place where they were excavated) describing the heads, and two others mentioning a previous treatment in 1965 with an adhesive called Vinylite.  Other information about these objects came from our curators, who knew that the heads are from the site of Dendera, more precisely the mastaba of Adu II, excavated by Flinders Petrie, a famous British archaeologist. Moreover, the heads are from the Sixth dynasty (2374-2140 BCE). That’s all we knew about those two heads before beginning our work !

Let’s have a closer look at them…

Left: one of the wooden heads viewed in profile Right: a front view of the other wooden head

Left: one of the wooden heads viewed in profile.  Right: a front view of the other wooden head.

A long quest is ahead and we’re only starting to think about an appropriate conservation treatment. Indeed, before any scalpel reaches their surface, we need to gather as much information as possible about the artifacts. Stay tuned to hear more about our discoveries and the decisions that we make based on what we learn.